Hair relaxers generally fall into two categories: mix and no-mix. “Mix” relaxers generally require a two-component system of a cream base and an activator, which are combined prior to use. Darkwa et al., U.S. Pat. No. 5,679,327, which issued Oct. 21, 1997, describes a highly alkaline hair straightening emulsion of this variety. The emulsion described employs a combination of a strong nitrogenous organic base and an alkali metal hydroxide in the presence of an alkaline earth metal cation. While alkaline earth metal hydroxides are characteristically ineffective as permanent hair straighteners or relaxers, the combination with, preferably, lithium hydroxide, is effective for achieving permanent straightening of hair with a treatment time not more than about 30 minutes. So-called “no-mix” relaxers on the other hand are ready to use. They generally are in the form of a liquid, cream, gel, paste or emulsion which can be directly applied to a subject's hair without first, as the term implies, mixing of two or more separate components.
No mix hair relaxers are very convenient and therefore very desirable. However, they suffer from many of the same problems as their mix based counterparts and some which are unique. Some hair relaxers rely on strong organic and/or inorganic bases such as sodium hydroxide (also referred to as lye) to break the disulfide bonds found in hair's structure, thus allowing straightening through the application of mechanical forces. However, in the concentrations used, these strong bases generally exist at a pH of greater than 13.2, a level that is caustic and can be dangerous to unprotected skin if exposed for any great length of time. Even when skin is properly protected and a relaxer is properly formulated, hair relaxers with lye, for example, can become uncomfortable for subjects in as little as about 15 minutes. This can result in premature termination of the treatment, which often affects the degree to which hair can be straightened. And while higher concentrations and higher pH formulations can act more quickly, the amount of discomfort and the length of time that a subject could be exposed to the relaxer vary accordingly. Moreover, lye based products, because of their highly corrosive nature, can be very damaging to the hair, causing breakage and discoloration, as well as the general lack of desirable physical appearance.
Other strong inorganic bases have been used in place of sodium hydroxide. One of the most popular is lithium hydroxide. Lithium hydroxide, at appropriate concentrations, results in a lower pH and therefore is more comfortable and can be applied for longer periods of time. However, lithium hydroxide is not nearly as efficient as sodium hydroxide in obtaining appropriate degrees of hair straightening. The result is the need to expose the subject to a lithium hydroxide based hair relaxer for a longer period of time to achieve similar straightening. This, however, is self defeating. First, subject is drastically inconvenienced as treatment times of greater than 30 minutes are often required. Moreover, although more comfortable in the short term, upon longer exposure times necessary to obtain appropriate straightening, subjects often complain of scalp discomfort and burning sensations before the ideal treatment time has elapsed. Interrupting treatment at that point yields suboptimal results.
Still another problem is that the natural color or tint of the user's hair can be altered. For example, if the user's hair is initially naturally gray in color, treatment can result in a visible yellowing of the hair. Such discoloration is undesirable. For example, a yellow tinge on gray hair is particularly undesirable because the white fibers in gray hair normally have a desirable natural bright tone which gives the hair highlights, whereas, when yellowed, this same hair looks dull, drab and lacks luster.
Permanent hair straightening should be achieved as quickly as possible to minimize skin irritation, hair damage, and/or hair discoloration from exposure to alkali. For persons having a “fine” type of hair, this can be generally readily achieved. However, for persons having “normal” and especially “coarse to resistant” hair, generally longer treatment (contact) times or greater concentrations of alkaline material or both are needed to effect permanent hair straightening. It is generally recognized in the hair straightening art that prolonged exposure (contact) of hair to the highly alkaline conditions required for permanent hair straightening increases the possibilities of irritating the scalp and hair line skin, of weakening the strength of the treated hair, and of hair discoloration. Thus, even though the extent of permanent hair straightening tends to improve in direct proportion to increased alkalinity and treatment (contact) time, so does the advent or likelihood of these adverse, undesired problems. To avoid or minimize such problems, it is common to limit the treatment time (that is, the time of contact between the emulsion and the user's scalp and hair) to a period that is not longer than about 30 minutes as is known to those familiar with the art.
In addition to these concerns, no-mix formulations must be storage stable and ready to go at a moment's notice. However, oxygen and/or moisture can seep into packaging, which can react with the hydroxide species, reducing potency and efficacy. Providing completely moisture proof packaging is possible. However, that would be very expensive. Therefore, something needs to be done to protect no-mix relaxers and to ensure potency and efficacy at time of use.
Add to these problems the significant problems of ensuring that the product has the right consistency, is easy to apply and remove, is pleasant to work with for stylists who use it time and time again, day in and day out, and for clients as well. One can readily appreciate the difficulties in obtaining a safe, reliable, cost effective and desirable product.
Perhaps because of their respective associated highly alkaline pH (the usual range being as above-indicated), either one of such prior art types of permanent hair straightening emulsions can cause problems. One problem is that skin irritation can result, particularly when the prior art hair straightening emulsion is allowed to remain in contact with the user's hair or skin for more than an acceptable time period. Another problem is that the user's hair can become structurally weakened during treatment so that excessive hair breakage in the resulting straightened hair results.
There remains a substantial and long felt need for improved formulations which employ relatively lower pH levels and which can achieve substantially complete permanent hair straightening of naturally curly, previously untreated, and even coarse hair within a hair contact time period of not more than about 30 minutes. Preferably such improved formulations also demonstrate reduced skin irritation and are both easy and economical to produce and use. The present invention provides such formulations.